Astrometry of H2O masers in nearby star-forming regions with VERA III. IRAS 22198+6336 in lynds 1204G

Abstract

We present results of multi-epoch VLBI observations with VERA (VLBI Exploration of Radio Astrometry) of the 22 GHz H2O masers associated with a young stellar object (YSO) IRAS 22198+6336 in a dark cloud, L1204 G. Based on phase-referencing VLBI astrometry, we derived an annual parallax of IRAS 22198+6336 to be 1.309 ± 0.047 mas, corresponding to the distance of 764 ± 27 pc from the Sun. Although the most principal error source of our astrometry is attributed to the internal structure of the maser spots, we successfully reduced the errors in the derived annual parallax by employing position measurements for all of the 26 detected maser spots. Based on this result, we reanalyzed the spectral energy distribution of IRAS 22198+6336 and found that the bolometric luminosity and total mass of IRAS 22198+6336 are 450 L⊙ and 7 M⊙, respectively. These values are consistent with an intermediate-mass YSO deeply embedded in the dense dust core, which has been proposed to be an intermediatemass counterpart of a low-mass Class 0 source. In addition, we obtained absolute proper motions of the H 2O masers for the most blue-shifted components. We propose that the collimated jets aligned along the east-west direction are the most plausible explanation for the origin of the detected maser features. © 2008. Astronomical Society of Japan.